1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof. It is to be noted that in this specification, a semiconductor device refers to a semiconductor element itself or a device including a semiconductor element. Examples of such a semiconductor element include, for example, a thin film transistor. Accordingly, the semiconductor device also includes devices such as liquid crystal display devices.
2. Description of the Related Art
In recent years, semiconductor devices have been essential for human life. Semiconductor elements such as thin film transistors included in the semiconductor devices are manufactured by forming a thin film such as a semiconductor film on a substrate and processing the thin film into a desired shape. This type of manufacturing method has been also applied to, for example, liquid crystal display devices (for example, liquid crystal televisions).
For thin film transistors in conventional liquid crystal televisions, an amorphous silicon film has been often used as the semiconductor film. This is because a thin film transistor formed using an amorphous silicon film has a structure which can be relatively easily formed.
However, in view of the recent situation of moving images (for example, watching movies in 3D and watching sports in 3D), it has been difficult to express the sharpness of moving images in the case of liquid crystal televisions using amorphous silicon films, and the development of thin film transistors which show a fast response and have a high carrier mobility has been advanced. Therefore, the development of microcrystalline silicon films has been advanced (for example, Patent Document 1).